The present invention relates to a rotary compressor comprising an improved rotor lubrication system, and more particularly to a rotary compressor in which an oil separation function, provided in prior compressors by an oil separator component, is provided by a unique configuration of an outlet passageway.
A rotary compressor to which the present invention relates may be advantageously used to circulate a refrigerant fluid in an automotive or home air conditioning system and comprises a bored housing and a rotor eccentrically mounted in the bore. The rotor comprises a cylindrical rotor body formed with radial slots in which vanes are slidably retained. In past rotary compressor designs an oil pump is provided to circulate oil from an oil sump to the rotor and rotor bearings for lubrication thereof. In an improved compressor of the present type, no oil pump is necessary and the oil circulation function is performed by means of the pressure difference between the inlet and outlet of the compressor. Specifically, the outlet communicates with the oil sump so that the oil in the sump is pressurized by the high outlet fluid pressure. An oil passageway leads from the oil sump through the interior of the rotor to the inlet so that oil is forced to flow from the oil sump through the rotor and rotor bearings to the low pressure inlet, thereby lubricating the areas of sliding contact between the vanes and the slots and also urging the vanes into sealing engagement with the bore wall. At the inlet, the oil becomes entrained in the refrigerant or working fluid and is sucked into the bore thereby lubricating the areas of sliding contact between the ends of the vanes and the bore wall. The working fluid and oil are subsequently displaced from the bore at elevated pressure to the outlet.
If the oil were allowed to be circulated in the external refrigerant system along with the working fluid which may be FREON (trademark) or the like, it would interfere with heat exchange in the condenser and evaporator and also increase the flow resistance of the fluid mixture, both being adverse effects in an air conditioning system.
It has therefore been a conventional expedient to provide an oil separator component to separate the oil from the refrigerant fluid at the compressor outlet and return the oil to the oil sump. There are two types of oil separators in common use, one type comprising a metal gauze and another type comprising a diverging conduit which causes the flow velocity of the fluid mixture to decrease rapidly enough to separate the oil from the working fluid.
The metal gauze oil separator constitutes a flow restriction which is adverse to the action of the compressor and has a strong tendency to become clogged. In addition, the metal gauze must be replaced periodically.
the diverging conduit type oil separator suffers from the disadvantage that the conduit must be precisely proportioned in order to produce effective oil separation and is therefore a rather expensive component to manufacture. A further disadvantage is that the velocity drop in the oil separator is not compatible with the overall operation of the compressor and external refrigerant circuit.